The present invention relates to a projection type image display apparatus, and more particularly to polarization splitting technology for polarization splitting of light emitted to a light valve such as a liquid crystal panel and light modulated by the light valve.
Technology related to the present invention is described in, for example, JP-A-2001-142028, JP-A-2003-131212 and JP-A-2003-195223 (corresponding to US 2003/0081317).
Japanese Patent Application Laid-Open Publication No. 2001-142028 describes as polarization splitting means a PBS prism having a polarized beam splitter (hereinafter referred to as “PBS”) which is a dielectric multi-layer film formed between the interfaces of two rectangular prisms.
Japanese Patent Application Laid-Open Publication No. 2003-131212 describes a wire grid type polarization splitting element having a diffraction grid provided by forming wire grids (e.g., metallic wire grids) on a glass substrate at a prescribed pitch (forming cycle).
Japanese Patent Application Laid-Open Publication No. 2003-195223 indicates a prism having polarization splitting characteristics configured as described below. Specifically, a diffraction grid is sandwiched between a pair of diffraction grid base materials, and a prism base material is bonded to the surface, which is in contact with the diffraction grid, of each of the individual diffraction grid base materials and to the opposite surface with an adhesive layer interposed. And, a diffraction grid medium which has substantially the same refractive index as that of a pair of prism base materials is filled in the space formed by the diffraction grid and the diffraction grid base material.